Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
H, W = map(int, input().split())
walls = 0
S = [0] * H
for i in range(H):
    L = input()
    walls += L.count('#')
    S[i] = '#' + L + '#'
S = ['#' * (W+2)] + S + ['#' * (W+2)]
V = [[0] * (W+2) for _ in range(H+2)]

q = [(1, 1, 1)]
while q:
    x, y, c = q.pop(0)

    if (x, y) == (H, W):
        # 最短経路と元々の壁以外を数える
        print(H * W - walls - c)
        break

    for m, n in {(0, 1), (0, -1), (1, 0), (-1, 0)}:
        i, j = x+m, y+n
        if S[i][j] == '#' or V[i][j]:
            continue
        q.append((i, j, c+1))
        V[i][j] = 1

else:
    print(-1)